1. Field of the Invention
Proposed inventions are related to area of analytical chemistry, namely to a chromatography and to fabrication methods of the chromatography equipment elements, more concrete—to the chromatographic column and method of its manufacturing.
2. Description of Related Art
One of modern tendencies of analytical chemistry is a miniaturization of chromatographic equipments, including use of capillary columns in the chromatography (Tesarszik K., Komarek K. Capillary columns in gas chromatography (in Russian—translation from Czech).—Moscow, Publishing house “Mir”, 1987, 222 p. [1]). Using the capillary columns with a sorbent located on internal walls has allowed to increase specific and general efficiency of achievable separation, to reduce sorbent consumption, to increase considerably sensitivity of chromatographic analytical system and to improve such characteristics of process as a radial gradient of temperature at programming, to simplify realization of hyphenated method of the gas chromatography analysis in a combination with mass-spectrometry.
Separation of substance sample on its components in a chromatography is determined by two characteristics of chromatographic column—its selectivity and efficiency. Measure of selectivity is relative retention of separated components, and measure of efficiency is characterized by number of so-called theoretical plates. Basic advantage of the chromatographic capillary columns is that on absolute and relative efficiency of these columns essentially surpass traditionally used chromatographic packed columns having diameter more then 2 mm. Total efficiency of capillary columns is 30000–100000 theoretical plates, and more (Rudenko B. A. Capillary chromatography (in Russian)—Moscow, Publishing house “Nauka”, 1978.—215 p. [2]) that much more surpasses efficiency of the packed columns.
Together with such advantage as high efficiency of sample components separation, chromatographic capillary columns have the disadvantage consisting in significant restriction of the sample's weight. It reduces a signal magnitude at the analysis and sharply increases the limit of determined concentration.
This advantage is reduced in polycapillary (multichannel) chromatographic columns, being a package of 1000–2000 capillaries of diameter from 30 up to 100 micrometers located in parallel to each other (the inventor's certificate of the USSR No968181, issued 15.08.91 [3]; inventor's certificate of the USSR No1635128, issued 15.03.91 [4]; patent of the Russian Federation No1651200, issued 23.05.91 [5]).
However, when the column has such limited number of capillaries, then even insignificant distinctions in amount of the deposited mobile phase in them result in occurrence of a significant dispersion of retention times of substances. The dispersion essentially reduces efficiency of separation achievable with the aid of such columns. As a result, the efficiency of such columns stops increase when their length surpasses 1.0–1.5 m.
In inventor's certificate of the USSR No1635128 (issued 15.03.91 [6]) the method of manufacturing polycapillary chromatographic columns is proposed. The method's purpose is increasing uniformity of the columns' flow areas. The method provides manufacturing a column by softening and drawing bank of blanks formed from cylindrical rods of identical size. The rods forming central part of the blank of each separate channel are made from a technological material, should be later removed. Rods, surrounding the central part, are produced from the base material. These rods after removing the technological material form a walls of the channel. A package of blanks is formed in a way, providing hexagonal or square packing the rods' group
Known method on the inventor's certificate of the USSR No1635129 (issued 15.03.91 [7]) in comparison with previous is more complicated. Some of the rods surrounding rods of the blank's central part of the single channel are also produced from the technological material. After removing the technological material, it results in formation of longitudinal grooves in walls of the channels. The grooves connect the joint channels with each other.
Thus, polycapillary chromatographic columns made by the methods, known from [6] and [7], contain set of the parallel channels. The channels are joined by fusion of external walls of the adjacent channels. At that in the column made by the method known from [6], channels are isolated from each other, and in a column known from [7] the adjacent channels are connected with each other by means of longitudinal grooves in their walls.
Polycapillary chromatographic columns made according to the specified methods require large labor-consumption. The large labor-consumption is caused by the necessity of manual forming the blank of each channel. At that, it is not possible to produce the blank having channels number exceeding provided in known columns [3–5]. Therefore, further increase of the chromatographic column parameters is impossible. Therefore, realization of advantage of the manufacturing methods known from [6, 7] is impossible too.
Polycapillary chromatographic column and method of its manufacturing known from the inventor's certificate of the USSR No1635128 [6] are closest to the proposed column and method.